The present invention relates to an internal combustion engine with a shutter device arranged in an exhaust conduit for regulating the exhaust counter-pressure in the engine cylinders during engine braking.
It is known that the engine braking power of a vehicle can be increased with the aid of a shutter in the engine exhaust manifold. This exhaust pressure regulator provides continuous variation between a completely open position and a completely closed position. In the closed position, a counter-pressure can be created during the exhaust stroke of the engine, so that a pressure of up to 3-4 bar is created in the engine cylinders and the exhaust manifold, which increases the braking power of the engine during the exhaust stroke. The exhaust pressure regulator can also be used when the exhaust system is put into communication with the cylinders during the latter portion of the inlet stroke to achieve an inner charging, thus increasing the compression work after cutting off the communication between the cylinders and the exhaust system.
Vehicles with engines having exhaust pressure regulators are practically without exception heavy vehicles, such as trucks and buses, which have a number of pneumatically controlled installations and systems, such as pneumatic brakes, air springs etc., which are supplied with compressed air from air tanks charged by an air compressor usually driven mechanically directly by the engine. The air compressor takes its intake air from the surrounding atmosphere. The greater the air requirements the air consumers have, the greater will be the required capacity of the compressor and the greater the power is which must be extracted from the engine. Vehicles requiring exceptionally great amounts of compressed air are for example buses, which must be braked many times for stopping at bus stops and traffic lights and which also have pneumatically operated doors. Buses with air suspensions, which "dip" at bus stops, have extra large air requirements.
By EP 0 335 086 it is previously known to control a compressed air compressor driven by the vehicle engine via clutch, depending on the operating state of the vehicle, so that the clutch is engaged for driving the compressor and charging a compressed-air tank, when the engine operation changes from driving to braking. In this manner, the kinetic energy of the vehicle is used to drive the compressor, and a portion of the braking energy, which is otherwise lost as heat in the vehicle brakes, is instead used to drive the compressor. In this manner, the operating time of the compressor when the engine is in drive mode, is reduced.